I don't get it, I stopped using shampoo for it because I know thats why it hurt the first time, but now I'm just using vitamin enriched lotion and it still hurts. And I'm drinking a lot of water to try to flush it out but it still hurts to sit down and I have to bend over for it to stop.
Just in case it is a reaction to what you are using, get some proper lube either something like KY petroleum jelly (avoid this with condoms as it will rot the latex). For better lube there are things like astroglide, silicon based lube and all sorts of others which are made for this purpose.
If, once you are using proper lube you still have problems, you just have to take it slowly, try not to do anything in the heat of excitement that might hurt when you are finished!!!! Dont use anything too big, and work up in size so that you are used to the smaller things before you go large!
There may also be a problem in your anus, you could have piles (hemorrhoids) which are being irritated by this so either get some ointment from the chemist or go to your doctor depending on how bad it is. Dont worry, people who never stimulate their anus get piles so you dont need to say you were doing this. just say you were constipated!!
I think ''Spunky'' just made a mistake adding the word ''petroleum'', Anywayz I don't understand your question? are you Gay? you male or female?
I don't know if that makes a differance with your back problem or not, but it may help other poster to help you better?
sounds like to me the stimulation maybe to deep or to rough, and also theres a possiblity you may have an infection of some kind?